AArch64: Remove AARCH64_EXTRA_TUNE_NO_LDP_STP_QREGS

AArch64: Remove AARCH64_EXTRA_TUNE_NO_LDP_STP_QREGS

Remove the tune AARCH64_EXTRA_TUNE_NO_LDP_STP_QREGS since it is only
used by an old core and doesn't properly support -Os.  SPECINT_2017
shows that removing it has no performance difference, while codesize
is reduced by 0.07%.

gcc/ChangeLog:
	* config/aarch64/aarch64.cc (aarch64_mode_valid_for_sched_fusion_p):
	Remove check for AARCH64_EXTRA_TUNE_NO_LDP_STP_QREGS.
	(aarch64_advsimd_ldp_stp_p): Likewise.
	(aarch64_stp_sequence_cost): Likewise.
	(aarch64_expand_cpymem): Likewise.
	(aarch64_expand_setmem): Likewise.
	* config/aarch64/aarch64-ldp-fusion.cc (ldp_operand_mode_ok_p):
	Likewise.
	* config/aarch64/aarch64-ldpstp.md: Likewise.
	* config/aarch64/aarch64-tuning-flags.def: Remove NO_LDP_STP_QREGS.
	* config/aarch64/tuning_models/emag.h: Likewise.
	* config/aarch64/tuning_models/xgene1.h: Likewise.

gcc/testsuite:
	* gcc.target/aarch64/ldp_stp_q_disable.c: Remove test.